Antenna



Aug. 2, 1938. C. A. NICKLE I 2,125,804

ANTENNA Filed May 25, 1934 Fig. l. Fig. 2. Pfg. 5. Figf. 2.3: -J'Zogz-y'lzp 2g :'/Z'g Zz: 0

y waff/v7# CURRENT FTQ 6 F/EL STRENGTH .40 quency at which the antennaoperates.

Patented Aug. 2, 1938 ANTENNA Cliord A. Nickle, Schenectady, N. Y.,assigner to General Electric Company, a corporation of New YorkApplication May 25, 1934, Serial No. 727,409

17, Claims.

` My invention relates to antennae and more particularly to antennaehaving a physical length less than sixty-four one-hundredths of a wavelength of the frequency at which theantennae operate.

One object of my invention is to provide means v whereby the efficiencyof such antennae is increased.

A further object of the invention is to provide means whereby wideflexibility is afforded in adjustment of the current distribution insuch an antenna so that practically any desired current distribution maybe obtained. It is a particular object of my invention. to provide meanswhereby the current may be elevated in the antenna, that is, whereby thecurrent maximum, or loop, may be caused to occur at a point high in theantenna, or even at the top. v

A still further object of my invention is to provide means wherebyground losses of the antenna are substantially reduced.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, both as to its organization and method of operation,together with further objects and advantages thereof may bestbeunderstood by reference to the following description taken in connectionwith the accompanying drawing in which Figs. l to 4 conventionallyillustrate my invention, Figs. 5 and 9 illustrate certaincharacteristics thereof, Fig. 6 illustrates a practical embodiment of myinvention and Figs. '7 and 8 illustrate certain modifications of myinvention. v

Referring to Figs. l to 4 inclusive of the drawing, I have shown in eachof these figures a vertical antenna which may be of any desired heightless than about one-half wave length of the fre- These antennae mayoperate either as transmitting antennae or receiving antennae and areconnected to the apparatus with` which they are associated throughcoupling means 2 which may be of any desired form but which isillustrated as a transformer. At the top of each antenna is shown an 'iinductance coil 3 which is connected between the top of the activeportion of the antenna, that is, that portion of the antenna which isexposed 50 with respect to radiant energy, and a capacitance area. Thiscapacitance area may have kany desired form. It may comprise thehorizontal portions of the ordinary L, T, or umbrella type antenna or itmay be a sphere, or cylinder closed, lif desired, at the vtop andenclosing the coil (Cl. Z-33) thereby to afford protection to the coilfrom the weather.

The use of capacitance areas at the top of a vertical antenna is ofcourse Well known. It has been found, however, that extremely importantadvantages may be obtained by the Vuse of a coil Y at the top of theantenna connected between the capacity area and the antenna, the coiland capacity area being properly proportioned to produce desired currentdistribution in the radiating portion of the antenna. Certain of theseadvantages are apparent from curves 5 and 6 of Figs. `1 to 4representing respectively the voltage and current distribution on theantenna produced by certain specific adjustments of the impedancecomprised by Vthe coil 3 and capacitance area 4 when used on a quarterwave antenna. In Figs. 1 and 2 this impedance is equal to the surgeimpedance of the antenna and is capacitive. That viS Y Z=jZ0 where Zrepresents the impedance of the coil and capacitance in series and Z0represents the surge impedance of the antennae.

In Fig. 3 the total impedance is equal to the surge impedance but isinductive and in Fig. 4 the total impedance is zero. That is, theinductance 3 resonates with the capacitance between area 4 and theearth, or the top of the antenna is short circuited to earth. In Figs. 1and 2 it will be observed that the current is equal at both ends of theantenna and is maximum in the middle. Since the antenna of these figuresis one-quarter of a wave-length long and the current is equal at bothends the electrical length of the antenna and top impedance is,therefore, three-eights of a wavelength. In Fig. 3 the current is equalat both ends and zero at the middle or at a point one-eighth of awavelength above the ground. The electrical length of the antenna plustop impedance is thus ve-eighths of a Wavelength. In Fig. 4 the currenthas a maximum at the top and is minimum at the base. Its electricallength is thus one-half of a wavelength.

The voltage distribution on the antennae is, of course, 90 displaced inphase with respect to the current distribution.

These particular values of the impedance placed at the top are chosenfor illustration purposes -only since any other distribution may beobtained by proper choice of value of inductance employed with respectto the capacity between the capacity area and earth. Further, it will beunderstood that my invention is in nowise limited to quarter waveantennae but is applicable to any antenna of less than .64 of awavelength in length, this dimension having been found to be theoptimuml height of a vertical antenna. In general, however, it will befound that when the antenna is of length in excess of a half wavelengththe desired value oi reactance at the top may be ob-y tained by the useof a capacity area without any neutralization by use of seriesinductance.

These values of impedance may be confirmed, and a better understandingof the invention had, by reference to the following consideration of my4invention.

We know from transmission line theory that the current at any point in atransmission line may be expressed by the following equation.

where iozcurrent at any point in the line ebzimpressed voltage 1):distance of the point from the end of the line expressed in degrees 0:total length of the line expressed in degrees Zzzimpedance in which theline is terminated Zozsurge impedance of the line `We also know that theVoltage and impedance at any point p in the line may be expressed by thefollowing equations.

lcs

Vthe antenna. v 1 Y et f NFO-Z2 cos H-i-jZn sin 0 (4) Similarly letting=0 in Equation 3 we get the following expression for current at thebottom of the antennae.

Since these two currents i are equal and of like polarity Z eb Jeb sin0+el, cos H Z2 sin 0 vadjusted to have for an antenna of any desiredlength to produce the current distribution in question. If the antennabe a quarter wave antenna 0=90 then Ynode along the length of theantenna.

If we wish the current distribution indicated by Fig. 3 then To producethe current distribution indicated in Fig. 4 it will be noted that thecurrent at the bottom is Zero. This means that'the impedance Z at thispoint is nnite or that the denominator of the right-hand term inEquation 3 is equal to zero, i. e.,

.Z2 iE sin dri-cos =O jZ2 sin :t: Z0 cos q,

Z2 Z() COt d) but since =0 in this case Since for a quarter wave antennaZ2=O (l0) That is, for minimum current at the bottom and maximum currentat the top of a quarter wave antenna the top of the antenna should beshort circuited to ground. This may be effected by adjusting the coil 3for resonance with the capacity between the capacity area and the earth.

Thus we have Equations 5, 7, and 9 by which we may calculate theimpedance necessary at the top of the antenna to produce currentdistributions correspondng to Figs. 1, 3, and 4 respectively forantennae of any length, and Equations 6, 8, and 10 respectively forquarter wave antennae.

By a similar process which will now be apparent to one skilled in theart the impedance at the top of the antenna necessary to produce adesired current distribution in an antenna of any length may readily becalculated.

My invention has the advantage that the desired current distribution maybe obtained without the use of any large or expensive structure to aiordthe necessary capacity at the top. That is, a portion, or all, of thereactance of the actual capacity existing between the capacity area andearth may be tuned out by the reactance of the inductance. Thus, forexample, for a quarter wave antenna any desired sinusoidal currentdistribution, including those with current loops high on the exposedportion of the antenna, as indicated by Figs. 1, 2 and 4, may beobtained by use of a sphere and a proper coil neither of which need beof objectionable dimensions.

If the antenna be one having a length less than one quarter of awavelength Z2 should be inductive to produce a current node along thelength of the antenna. If the antenna has a length greater than aquarter of a wavelength then Z2 should be capacitive to produce acurrent Of course in the latter case the purpose of the inductance is topermit a desired capacity reactance to be obtained without using anundesirably large capacitance area. That is, any excessive capacityreactance is neutralized by the inductive reactance. If minimum currentat the bottom is desired in an antenna of less than one quarterwavelength Zz is inductive, and if the antenna be of length greater thana quarter wavelength Z2 is capacitive.

In Fig. 5 I have illustrated certain characteristic curves made fromexperimentally obtained data and which illustrate the gain in eldstrength obtained by the use of my invention in a` radiating antenna.VThese curves were taken by exciting the antenna with constant power of7,150 kc. Curve A was made by observing the variation of iield strengthat a distant point on of the sphere to be used is also affected by thethe earth caused by variation of the height of a simple vertical wire.Curve B was obtained `in the same way except that the vertical wire hada sphere of 12 inches in diameter connected to the top. Curve C' wasobtained in the same way except that a coil was connected between thesphere and wire at the top and adjusted in each case to produce maximumeld strength. It will be observed from these curves that a verysubstantial gainin field strength is obtained by the use of myinvention. In fact, practically the same field intensity is` produced bya quarter wave antenna using my` invention as is produced by a half waveantenna of the simple vertical type. The gain resulting from myinvention is even greater for shorter antennae. 'I'hus my invention isof great importance in locations and under conditions where it isdesirable to avoid high antenna structures.

Of course the gain in eld strength produced by my invention is dependentupon the type of coil used and the size of the sphere, the iieldstrength increasing, in general, withincrease in size of the sphere. Anylosses in the coil, necessarily, detract from theV advantages gained bythe use of my invention and accordingly a. coil having minimum lossesis' desirable. In general the larger the power factor of the coil thesmaller the reactance of the capacity produced by the area 4 shouldbe.vFor example, for antennae having a length between 1/8 and 1A; of awavelength if the coil` has a power factor of .0025 the reactance ofthecapacity should not exceed 2,500 ohms. If the power factor of the coilbe .005 the reactanceof the capacitance shouldnot'exceed 1,250 ohms, andif the power factor be .0l the reactance should not exceed 625 ohms; Thesize ground resistance. For example, if the ground resistance be highthe gain resulting from the use of my invention is greater than would bethe case were the ground resistance low. This is by reason of theincreased reduction of losses in the high, marked gain may be securedbythe use of a relatively small sphere.

The gain in field strength produced by my invention is believed to bedue rst'to the reduction of current in the ground connection therebyreducing ground losses and permitting more of the power supplied to theantenna to be consumed in radiation. The second reason for the increasein eld strength is believed to be in the change in radiation resistanceat the current loop, that is, at the point in the antenna of maximumcurrent. For a quarter wave antenna operating with maximum current atthe top, as shown for example in Fig. 4, the loop radiation resistanceis approximately 32 ohms in contrast to the usual quarter wave antennaresistanceof 36 ohms. This accounts for approximately `51/2v% increasein ground wave eld intensity.

Consider, for example, a simple vertical antenna of the quarter wavetype having a ground resistance of 10 ohmsand a loop radiationresistance of 36 ohms. In such a system if 100 Watts z-be supplied tothe antenna 78 watts are radiated whereas 22 watts are lost in theground connection. This may be considered to produce a eld strength of\/78 or .883 units at a certain distance from the antenna. On the otherhand, if we assume that the antenna be tuned for maximum current at thetop and that the ground resistancebe still l ohms, 98 watts are thenavailable for radiation, whereas only 2 watts are lost in the ground.Under these conditions the field strengthV will be 1.055\/% or 1.045units or an improvement in eld strength of about 19 percent. This meansabout a 40 percent increase in received power at any remote point.

An antenna tuned as illustrated in Fig. 4 is to be preferred forbroadcast service, for example, where it is desired to produce a maximumof radiation horizontally, i. e. a maximum of eld strength in the groundwave. A current distribution of the kind shown in Fig. 3 may be usedwhere a high angle radiation is desired. In Figs. 1 and 2 the radiationis horizontal with a greater proportion of sky wave than is obtained bythe current distribution of Fig. 4.

Since it is an object of my invention to obtain these effectsV by reasonof desired `current distribution it will be understood that Icontemplate the use of an antenna having suflicient length relative tothe wavelength at which it operates that the current distribution alongthe length of the antenna may determine the direction in Vwhich wavesare radiated from the antenna into space, or `the direction in spacefrom which waves are received upon the antenna. not true to any materialdegree in very short antennae such as antennae of length less thanonesix'teenth of a wavelength of the wave at which they operate. In suchantenna, irrespective of the portion of the standing wave of currentwhich exists on the antenna the wave is radiated in substantially thesame direction. I therefore contemplate the use of my invention inconnection with antennae having actual lengths between ,1-6 and i4/100of the wave at which they operate.

It 4will be observed that in Fig. 2 a second capacity area 5 tuned bymeans` of a coil il is connected to the base of the antenna just abovecoupling device 2. This device serves to carry the reactive component ofthe antenna current to ground. That is, in any antenna on whichl thevoltage node, or antinode, is above the ground there exist reactivevoltamperes at the base of the antenna. The reactance of the unit 5, 6may then be adjusted relative to the impedance looking into the `antennato cause this unit to carry the entire reactive current. In other words,the reactive impedance to ground of this device is vequal and oppositeto that looking into the antenna. In this way only energy current issupplied by transformer 2. With a current distribution like `that inFig. 2 the impedance of unit 5, 6 is equal to that of the unit 3, 4 atthe top of the antenna. This device thus obviates concentrated currentin the ground and reduces ground losses. i

In Fig. 6 I have shown one practical embodiment of my invention in anantenna of the tower type. In this figure I have represented at 'l thetop of a tower antenna. The coil 3 is arranged within the structure ofthe tower top, the bottom of the coil being connected to the towerstructure and' the top of the coil being connected to a conductingmember 8 extending to a capacity area 9 arranged above the top of thetower. This capacity area 9 and conductor This iS 8 are insulated fromthe tower by means of an insulating member I0. The capacity area 9 maybe of any suitable structure and size and, by reason of my invention,need not be objectionably large. A shield I2 is shown supported from theconducting member 8 and surrounding the coil 3 whereby the coil isshielded from the metallic portion of the tower.

This embodiment of my invention is described and claimed in anapplication Serial No. 727,419, Patent No. 2,059,186, October 27,' 1936,entitled Antenna structure, filed simultaneously by W. W. Brown andassigned to the same assignee as my present application.

Some inconvenience in the use of my invention results from thedesirability of adjusting the coil which is located at the top of theantenna. To obviate this diiculty, structures have been proposedrof thekind shown in Figs.,7 and 8 in which an additional conductor I6 isarranged in parallel with the vertical antenna, this conductor and thevertical antenna forming a transmission line. This form of my inventionis described and claimed in a copending application, Serial No. 727,437,Patent No. 2,101,674, December 7, 1937, entitled Antenna, ledsimultaneously herewith by Robert B. Dome, and assigned to the sameassignee as my present application. In Fig. 7 the conductor is shownconnected to the base of the vertical antenna through a variableimpedance I'I and in Fig. 8 it is shown connected to the verticalantenna by a jumper I8 which may be movable upwardly and downwardlyalong the length of the antenna.

It is well known from transmission `line theory that the impedancelooking to the open end of a transmission line may be varied either byvarying the impedance at the opposite end of the transmission line or byvariation ofV the length of the transmission line'. Thus, for example,in Fig. 7 the inductance looking into the top of the transmission linemay be varied if desired by variation of the inductance I'I located atthe base. 'Ihus in this way an effective inductanceis produced at thetop of the antenna by the use of the conductor I6 and inductance IIwhich is variable as desired from the ground. In Fig. 8 the same effectis produced by variation of the jumper I8 upwardly or downwardly alongvthe length of the antenna.

It has been found, however, in the use of such a system that a verylarge current flows in the transmission line at the base of the antenna,that is, in the inductance I'I or the jumper I8. To reduce this currentit is proposed to divide the require inductance. at the top oftheantenna into a fixed portion and a variable portion, the fixedportion being arranged at the top of the antenna` as indicated at I9 inFigs. `7 and 8 and the variable portion being produced'by use of' thetransmission line and connections I'I and I8 as previously described.

In Fig. 91' have shown certain relations obtained from experimental dataon an antenna of the type shown in Fig. 8 with the exception that thefixed inductance I9 at the top of the antenna was not employed, theentire inductance at the top being made up by use of the transmissionlineY conductor I6 and jumper I8 in connection with antenna I. Thesecurves are plotted to logarithmic coordinates and pertain to an antennaexcited by the frequency of 7,150 kc and having a height of 408 inchesor slightly less than a quarter of a wavelength, and having a 12-inchsphere at the top. As' the jumper was moved from the ground to a heightof 400 inches the top current was found to reduce in a manner indicatedby the curve D at a progressively decreasing rate. The base current wasfound iirst to decrease to a minimum value and then to increase as shownby the curve E, whereas the iield strength at rst rapidly increased to amaximum value and subsequently decreased.

It will thus be seen that the variation in field strength, base andtopcurrent is highly critical over a certain relatively narrow range ofvariation in inductance and is less critical at smaller values ofinductance. However, the adjustment for maximum eld intensity is notcritical unless the adjustment be made very close to the value whichproduces minimum current at the base. It will further be observed that asubstantial gain in eld intensity is produced with an adjustment whichproduces equal currents at the top and base of the antenna, or at evensmaller values of inductance.

It will be observed from Fig. 9 that with the jumper I8 at the top ofthe antenna where the transmission line adds no inductance the currentat the top of the antenna is small relative to that at the base. Sincethe antenna is a quarter wavelength long loaded by capacity at the top anode of current occurs at the top and another substantially che-quarterof a wavelength below the base. Upon moving the jumper down the firstchanges in inductance have little effect on the current distribution.Further increases in the inductance cause the top current to increaseand the base current to reduce until they become of equal value. Theantenna is now longer than before by reason of the added inductance, i.e., a larger portion of a. wavelength Vnow appears on the inductance andradiator, this portion being three-eighths of a wavelength as isapparent from the equal currents at the top and base. Thus the lowernode has moved upward one-eighth of a Wavelength and now exists onlyone-eighth of a wavelength below ground. The current distribution isthus that illustrated in Figs. 1 and 2 and it will be observed fromcurve F of Fig. 9 that the field intensity at a distant point on theearth is rnearly a maximum. As the inductance is increased by moving thejumper downward the eld intensity attains a maximum as indicated bycurve F. The top current increases and the bottom current decreases to aratio of about .56 as measured from Fig. 9. The nodal point is stillbelow the base, since a minimum of current at the base has not beenattained, by about .08 of a wavelength as may be readily computed fromthe ratio .56 of currents at the base and top. The electrical length ofthe antenna is now V.42 of a wavelength. Upon further movement of thejumper downward a minimum, or nodal point, of current at the base isattained with large current at the top and a slight reductionfin fieldstrength at the distant point. The electrical length is now .5wavelength.

Upon further increase in inductance the current increases at the base ofthe antenna the electrical length of the antenna having increased beyondone-half wavelength and the nodal point of current having now risenabove ground. It is noted, however, that the current at the top alsoincreases. This is by reason of reduction in radiation resistance of theantenna when its electrical length increases beyond a half wavelength.It will also be observed that the eld strength at a distant point on theearth reduces.

alsl

This is due to increased current and hence iny ance from zero causes thecurrent distribution to be changed from that of an antenna having anelectrical length of one-quarter of a wavelength through thatcorresponding to one having an electrical length three-eighths of awavelength (Figs. l and 2) to that ofan antenna having length equal toor greater than. one-half of a wavelength (Fig. 4). Fig. 3 shows thenodal point moved upward to the middle of a quarter wave antenna wherebythe electrical length is five-eighths of a wavelength. Thus any desiredcurrent distribution may be obtained.

It has been found experimentally that practically these same relationsobtain in an antenna of the type shown in Figs. l to 4 if the inductanceat the top be varied over a wide range.

It will, of course, be understood that the forms of my inventiondescribed herein are set forth by way of clearly illustrating theprinciples involved and that various modifications of my invention willoccur to a person skilled in the art. I, of course, contemplate by theappended claims to cover any such modications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent in the UnitedStates, is:

l.. The combination of a vertical antenna having a pdrtion exposed withrespect to radiant energy, the length of said portion being not greaterthan one quarter of a wavelength of the frequency at which the antennaoperates, and an impedance connected between the top of said portion andthe earth having a value such that a nodal point of current occurs alongthe length of said portion and between the ends thereof, said nodalpoint being positioned to produce maximum radiation in a desireddirection in the vertical plane.

2. The combination of a Vertical antenna having a length not greaterthan one quarter of a wavelength of the frequency at which the antennaoperates, a connection between the base of said antenna and the earth,and an additional connection between the earth and the top of saidantenna, and means to cause said additional connection to carry currentgreater than the current flowing between the base of said antenna andthe earth.

3. In combination, a vertical grounded antenna having a length less than.64 of a wavelength of the frequency at which the antenna operates and aconductive path, other than said antenna, extending between the top ofsaid antenna and the earth said conductive path comprising a reactiveimpedance having a value approximately l-cos Z0( sin 0 where Z0 is thesurge impedance of the antenna and 0 is the length of the antennaexpressed in degrees.

4. In combination, a vertical grounded antenna having a length less than.64 of a wavelength of the frequency at which the antenna operates and aconductive path, other than said antenna, extending between the top ofsaid antenna and the earth, said conductive path comprising a reactiveimpedance having a value approximately Z0 cot 0 where Z0 is the surgeimpedance of the antenna and 0 is the length of the antenna expressed indegrees.

5. In combination, a vertical grounded antenna having a length notgreater than a quarter of a wavelength, a conductive path other thansaid antenna, extending between the top of said antenna and the earth,vsaid path having an impedance, which is so, proportioned relative tothe length of the antenna and. its surge impedance as to produce acurrent maximum relatively high on the antenna and maximum radiationhorizontally.

6. A vertical antenna having a reactance con? nected between its topmostend and ground equal to the surge impedance of the antenna, saidreactance being included in apath between said topmost end and groundother than through said antenna.

7. A vertical antenna, a capacitance area at the top of said antenna, aninductance con- -nected between said capacitance area and said antenna,said inductance having such a value that the effective series reactanceof said inductance and the capacity between said capacity area andground are such as to produce infinite impedance at a point along thelength of said vertical antenna. the length of said vertical antennabeing suiiiciently great that the direction of maximum radiation isdependent upon the position of said point of infinite impedance and saidpoint of infinite impedance being positioned to produce maximumradiation in a desired rection in the vertical plane.

8. A vertical grounded antenna having a length not greater than onequarter of a wavelength, and means so constructed and arranged that theimpedance existing between the topmost point thereof and ground isinductive.

9. In combination, a vertical grounded antenna, and an impedanceconnected between the top thereof and the ground adjusted to a value onthe base current-impedance characteristic where the base current variesover a relatively large range upon any substantial change in saidimpedance.

10. In combination, an antenna, a high frequency circuit connectedbetween said antenna and ground, and a path between said antenna andground across said high frequency circuit, said path having reactancesubstantially equal and opposite to that looking into said antenna, saidpath including in series the capacitance between earth and a capacityarea of suicient dimensions to obviate concentrated ground current,

11. In combination, an antenna having a vertical portion exposed withrespect to radiant energy, said portion having a length not greater thana quarter of a wavelength of the oscillations at which the antennaoperates, a connection between the base of said portion and the earth,and a second connection between the top of said portion and the earth,said second connection having an impedance of such a value as to producea current node between the ends of said exposed portion of the antennaand positioned to produce maximum radiation in a desired direction.

12. In combination, a vertical antenna having a length not greater thana quarter of a wavelength of the frequency at which the antennaoperates, high frequency apparatus connected to said antenna, and meansto produce a nodal point of current along the length of said antennabetween the upper end thereof and the point of connection of saidantenna with said high frequency apparatus and at such a point as toproduce maximum radiation at high altitudes.

13. In combination, a vertical antenna having a capacity area at thetop, an inductance, the top of said antenna being connected to saidcapacity area through said inductance and said inductance having such avalue that the series impedance of said inductance and the capacitybetween said capacity area and the earth, is inductively reactive.

V141. The combination, in a vertical antenna having a length betweenone-sixteenth and sixtyfour one-hundredths of a Wavelength of the waveat which the antenna operates, a capacity area connected to the top ofsaid anten-na and a coil included in the connection between the top ofsaid antenna and said capacity area, said coil being so proportionedrelative to said capacity area that the current at a point on saidantenna substantially above the base is substantially greater than thecurrent at the base of said antenna thereby to direct radiation fromsaid antenna in a desired direction in the vertical plane.

V15. The combination of a vertical antenna having an actual height lessthan sixty-four onehundredths of the wavelength at which said an tennaoperates and greater than one-sixteenth of said Wavelength, highVfrequency apparatus connected to said antenna near the base thereof,said base being connected to ground, and means to direct radiation fromsaid antenna in a desired direction in the vertical plane, said meansincluding means to produce a point of minimum current along the lengthof said antenna between the ends thereof, and comprising a capacity areaat the top of said antenna, and an inductance connected between saidcapacity area and top.

16. An antenna comprising a vertical section one-quarter of the lengthof the communication Wave, a connection from the bottom of said verticalsection to ground, a capacity element at the top of said verticalsection, and an inductance serially connected between said verticalsection and capacity lelement and also located at the top of saidvertical section, said inductance having such a value as to make theeffective electrical length of said antenna equal to 0.58 of the lengthof the communication wave, whereby there is obtained a reversal in signin the current distribution at a distanceof 0.08 of the working Waveabove ground.

17. An antenna comprising a vertical section of a given physical length,appreciably less than 0.64 wavelength, a capacity element at the top ofsaid vertical section, and an inductance serially connected between saidVertical section and capacity element and also located at the top ofsaid vertical section, said inductance having such a value as to makethe effective electrical length of said antenna greater than thephysical length of the vertical section but less than 0.64 Wavelengthand such as to result in maximum radiation horizontally.

CLIFFORD A. NICKLE.

